The gynandroblastoma is an extremely rare sexual cord stromal tumor, which contains both male and female elements, characterized by Sertoli or Leydig cells and granulose cells. We describe an ovarian gynandroblastoma in a 28 year-old female patient, found accidentally during a cesarean section operation. There is only one reported case in world literature occurring in a pregnant woman. The principal component we found was adult granulose cells, with a microfollicular pattern, and the presence of luteinized cells in some areas; besides we found the presence of well differentiated Sertoli cells elements, in addition to Leydig cells groups, in over 10% of the tumoral surface. Inmunohistochemical stainings were performed: citokeratin, which resulted positive in Sertoli cells and negative in granulose cells; and inhibin, which was positive in both components showing its mixed origin.